A 41-year-old, first-time candidate, Cruz walloped the well-funded Republican establishment candidate, Texas Lt. Gov. David Dewhurst, in Tuesday's GOP Senate primary runoff. He did so by vowing to stand by his tea party principles.

"Politicians cut deals; principled conservatives deliver," is the way a Cruz television ad summed up his message.

Democratic Senate leaders reacted to Cruz's primary win with a warning: If he wins the general election in November, gridlock in the Senate will be even worse than it is now.

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"Anyone elected to the Senate who starts off by saying 'I won't compromise' isn't going to help us," Senate Majority Whip Dick Durbin told CNN.

The tea party movement is a good foil for Democrats, but the reality is Cruz's vote probably wouldn't make that much difference, because he's replacing Republican Kay Bailey Hutchison, and she votes with the GOP 90 percent of the time.

Still, Democrats do have a point that Cruz, like any senator, would have a lot of power to grind business to a halt.

"You know what the Senate is like," said Durbin. "One senator stands up and says no, we stop the train, until we figure out how to bring that senator around."

And Cruz wouldn't be the only possible new senator willing to do that. In Indiana, Richard Mourdock beat veteran Republican incumbent Sen. Richard Lugar, vowing confrontation over compromise.

"What I've said is, and what I continue to believe, certainly, is one side or the other must prevail. And I'm hoping this candidacy will help move the Republican Party forward to become a permanent majority," Mourdock said the day before his GOP primary win in May.

The Senate was already bound to be a more polarized place next year because so many moderates chose to leave. Nearly half a dozen from both parties are retiring this year, including Sen. Olympia Snowe, R-Maine; Sen. Joe Lieberman, I-Connecticut; Sen. Ben Nelson, D-Nebraska; Sen. Kent Conrad, D-North Dakota and Sen. Jim Webb, D-Virginia.

Still, it's an open question whether tea party rhetoric on the campaign trail translates into action in office.

Ron Bonjean was a Senate Republican leadership aide for years, and he said history shows leaders can never be sure what rank and file firebrands like Cruz will do.

"Ted Cruz is going to be a new voice, and he's going to be a variable that we don't know what to expect (from) yet," said Bonjean. "He can hold everything up if he wants to or he can go against the Senate Republican leadership."

Two years ago, a handful of successful tea party-backed Senate candidates promised to hold their own leadership's feet to the fire to slash spending, shrink the government and protect civil liberties. Sen. Mike Lee, R-Utah; Sen. Ron Johnson, R-Wisconsin; Sen. Rand Paul, R-Kentucky; and others beat party favorites by vowing to shake up the Republican establishment once in Washington.

But once they became senators, uncompromising demands were rare.

Last year, Paul sounded off against his GOP leadership and held up Senate passage of a bill extending parts of the Patriot Act.

But, by and large, the so-called tea party threat of halting business to make a point didn't often bear itself out.

"If you look at conservatives across the board, in the past year or so, there hasn't been a whole sea change that we thought would happen," said Bonjean.

Sen. Jim DeMint, R-South Carolina, is a sort of tea party kingmaker. Much to the chagrin of his party leadership, in 2010 he helped defeat GOP candidates across the country that Republican leaders supported.

That streak continues this year with Cruz. DeMint told CNN the political action committee he started and still advises gave Cruz $2 million in addition to critical help with the conservative grassroots.

DeMint argues the more tea party movement-backed senators, the less gridlock.

"(When) Ted Cruz comes in ... I think he can help empower some of the Democrats to make those hard decisions," DeMint told CNN.

The South Carolina lawmaker believes the more staunch conservatives in the Senate, the more Democrats will be forced to compromise and come the GOP's way.

"I think there are enough Democrats, if we have a strong mandate election, who will work with people like Ted Cruz and (Sen.) Marco Rubio and (Sen.) Pat Toomey and these senators here, in a sensible way to change the course of our country," said DeMint. "The good news is this: because the rest of the world is in such bad shape, if we make a few hard decisions about fixing our tax code, fixing our entitlements so that we're on a sustainable course, America could be the best place to do business overnight."

One thing is clear: if the GOP succeeds in winning back control of the Senate, expectations will be a lot higher and pressure on the Republican leadership will be a lot more intense not to give in on the "stick-to-our principles" sensibilities driving voters towards tea party-backed candidates like Cruz.

Sen. John Cornyn, R-Texas, is the man in charge of electing enough Republicans to the Senate to take the majority. In a Capitol hallway conversation, even he nodded and smiled in agreement with the notion that it's a lot easier to coordinate and control the caucus when you're in the majority.

It's a problem he and Sen. Mitch McConnell, the current Senate minority leader, relish having.